There was actually a really cool panel at the last Bubonicon where John Picacio talked with a bunch of writers (myself included) about covers we liked and issues of design. Part of what's happening these days is that covers are being designed to be eye-catching at thumbnail sizes. I think both these designs are particularly aware of that.

@Daniel Abraham.Interesting, I hadn't known that. Guess it makes sense considering the rise of ebooks and the fact that you may only be able to see a thumbnail sized image on the spine of a book when it's placed in a bookshelf. Any other reasons why this change is taking place?

Between ebooks and the increasing drive to buy things online. Even if you're picking up a physical copy from Amazon or the B&N site, the effectiveness in catching people's eyes is still going to be in a smaller format.